The　badminton　gymnasium　of　Beijing　University　of　Technology　is　the　main　built　gymnasium　for　Olympic　Games　in　2008　in　Beijing.　Based　on　the　design　requirement,　the　velocity　in　the　playing-field　should　be　less　than　0.2m/s　in　the　region　of　9m　above　the　playing-fields　ground.　To　guarantee　the　design　requirement,　this　paper　uses　the　methods　of　Computational　Fluid　Dynamics　(CFD)　technology　and　field　test　to　optimize　and　modify　the　original　design　of　the　cavity＇s　structure.　After　optimization　and　modification,　plenum　makes　obvious　sense　on　air　distribution　of　structure　of　the　cavity,　which　guarantees　the　9100　swirl　diffusers　uniform　air　supply　under　the　grandstand　seats,　the　velocity　in　the　playing-field　is　less　than　0.2m/s,　which　meets　the　design　requirement.　The　results　can　be　referred　to　optimization　design　of　air-conditioning　ventilation　system　in　large　badminton　gymnasiums.　©　(2014)　Trans　Tech　Publications,　Switzerland.